NxN parallel optical transceiver

ABSTRACT

An N×N parallel optical transceiver includes a printed circuit board, a laser driving control chip, one or more lasers, two GRIN lenses, an optical band-pass filter, a multimode fiber array and a photodiode array. In the transmitter, laser beams of the same wavelength simultaneously output from the laser chip are first focused by the first GRIN lens, then the beams pass through a wavelength band-pass filter and are refocused by the second GRIN lens, and enter the channels in the multimode fiber array. In the receiver, laser beams of a different wavelength from the multimode fiber array are focused by the second GRIN lens, then reflected by the band-pass filter, refocused by the second GRIN lens, and received by the photodiode array. The multi-channel parallel transceiver has a small form, and can integrate a DFB or FP laser chip and GRIN lenses.

FIELD OF THE INVENTION

The present invention generally relates to the field of (optical) fibercommunication. More specifically, embodiments of the present inventionpertain to parallel optical transceivers, methods of making and usingthe same, and systems including the same.

DISCUSSION OF THE BACKGROUND

As one implementation of high speed optical transmission, an advantageof parallel optical transceiving (e.g., optical signal transmission andreception) lies in technology and cost. Parallel optical transceivingutilizes intermediate, high speed photoelectric technology and repeating(e.g., multiple) channels to achieve a high speed, large capacitytransmission. Particularly, in short-distance communication, such asinterconnection between backplanes in a large communication system anddata transmission within a local area network, parallel opticaltransceiving is characterized in that it has a high transmission speed,small size, low weight, low crosstalk, etc. Driven by wirelesscommunication, video, voice service, etc., a communication solution ofhigher speed, larger capacity and longer distance is requested and/ordesired.

In conventional parallel optical transceivers, VCSELs (Vertical CavitySurface Emitting Laser) are used as optical signal sources. As limitedby the material(s) and the manufacturing technique(s), VCSELs aresuitable for a waveband of 850 nm, but use at other wavelengths orwavebands has met challenges that have been difficult to overcome.Standard fiber transmission at 850 nm brings large loss(es) such thatconventional parallel optical transceivers having VCSELs are usedprimarily for short-distance transmission within a range of about300-500 meters, far below the requirement for data transmission and PONs(Passive Optical Networks).

Reference 1 (CN1665086A) discloses adding a gradient-index or gradedindex (GRIN) lens array into a VCSEL array coupled to a fiber array tosmoothly and continuously focus emergent rays on the access point of thefiber array. This design is relatively complicated, and appears to belimited to a parallel optical transmitter for a short-distancetransmission (less than 300 meters).

Reference 2 (EP1253450A2) discloses a design including three fibers andan optical portion, wherein the optical portion comprises two GRINlenses and a filter. Specifically, this design relates to wavelengthdivision multiplexing without parallel light waves. Moreover, thisoptical link design does not appear to be broadly applied or adapted.

SUMMARY OF THE INVENTION

This present invention is intended to improve or increase thetransmission distance and the applied range of conventional paralleloptical transceivers. The present invention provides a parallel opticaltransceiver (e.g., an N×N parallel optical transceiver), the opticaltransceiver comprising: a printed circuit board, a laser driving controlchip or circuit, one or more lasers (e.g., one or more laser chips), twoGRIN lenses, an optical (e.g., band-pass) filter, a multimode fiberarray, and a photodiode (PD) array. The printed circuit board may carryhigh frequency signals and be used as a base for other components of theoptical transceiver. One end of the printed circuit board includes asignal input interface (e.g., in the form of a “golden finger”). Thelaser driving control chip is configured to control the laser(s) and canbe directly integrated into or onto the printed circuit board. The twoGRIN lenses flank the optical filter, and at least one of the lenses isfixed to the printed circuit board (e.g., after active alignment). Inthe transmitter, which may include a first optical link, the laser(s)may be attached to the printed circuit board by flip chip bonding (e.g.,after active alignment), and provide N laser beams of the samewavelength at the same time (where N is an integer of at least 2). The Nbeams are focused by the first GRIN lens and pass through the opticalfilter (which may function or work as a band-pass filter to selectivelypass light from the laser of a selected or predetermined wavelength orband), then the N beams are refocused by the second GRIN lens, and enterN channels in the multimode fiber array. In the receiver, which has asecond optical link, N laser beams of the same wavelength from a numberof channels (e.g., N channels, where in one example, N is 4) in themultimode fiber array are focused by the second GRIN lens and reflectedby the surface of the filter, and the N reflected beams are refocused bythe second GRIN lens before entering the PD array. The light from thefiber array has a different wavelength or band from the light from thelaser(s).

The laser(s) may comprise a plurality of laser chips, and each of thelaser chips may comprise a distributed feedback (DFB) or Fabry-Perot(FP) laser chip.

The laser chips may be spaced apart from each other by 0.1 mm and/orhave a numerical aperture of 0.4 μm, and the laser chips may be spacedapart from the first GRIN lens by a distance of 0.5 mm.

The GRIN lenses may each comprise a cylindrical optical lens having arefractive index that varies along its radial axis, and the GRIN lensesmay smoothly focus the light from laser devices to the multimode fiberarray, as well as from the multimode fiber array to the photodiodearray.

The multimode fiber array may comprise one or more multi-fiber push-on(MPO) and/or MTP® standard connector interfaces, and may have one ormore dimensions and/or constructions defined by the MTP® and/or MPOstandard(s).

The PD array may comprise a 1×N linear array of photodiode chips. Ingeneral, PD chips are easier to couple to other component(s) in theoptical transceiver than lasers (e.g., laser diodes [LDs]).

The PD chips in such an array may be spaced apart from each other by0.15 mm, and the center distance between the PD array and the multimodefiber array is 0.7 mm.

The present invention further concerns a parallel optical transceiver,comprising a printed circuit board, a laser driving control chip, one ormore GRIN lenses, a band-pass filter, a multimode fiber array, and a PDarray. The printed circuit board may carry high frequency signals and beused as a base, and one end of the printed circuit board includes asignal input interface (e.g., a “golden finger”). The GRIN lens(es) andthe band-pass filter are fixed to the printed circuit board (e.g., afteractive alignment). One of the GRIN lenses focuses N laser beams from theN channels of the multimode fiber array, and the band-pass filterreflects the N laser beams from the multimode fiber array towards the PDarray. The N reflected laser beams are refocused by the one GRIN lensonto the PD array. The N reflected laser beams have a common (i.e., thesame) wavelength.

The present invention further concerns an N×N parallel opticaltransceiver, comprising a printed circuit board, a laser driving controlchip, two or more GRIN lenses, an optical and/or bandpass filter, and amultimode fiber array having N channels. The printed circuit board maybe used as a base for other components of the optical transceiver, andone end of the printed circuit board includes a signal input interface(e.g., including a “golden finger”). The optical transceiver may furthercomprise N lasers (e.g., laser chips), which may be attached to theprinted circuit board by flip chip bonding (e.g., after activealignment). The lasers are configured to provide laser beams having thesame wavelength. A first GRIN lens focuses the laser beams, and theoptical/band-pass filter passes the laser beams through to a second GRINlens (e.g., the optical/band-pass filter is transparent to thewavelength of the laser beams from the laser[s]). The second GRIN lensrefocuses the N laser beams on a location on or in the N channels of themultimode fiber array.

Relative to the background art, the present invention advantageouslyprovides multichannel long-distance parallel optical communicationswhich may use DFB or FP lasers and GRIN lenses, and may also achieveminiaturization and/or greater integration of corresponding componentsand/or devices. These and other advantages of the present invention willbecome readily apparent from the detailed description of variousembodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram showing an N×N parallel opticaltransceiver.

FIG. 2 is a diagram showing the optical link of an N×N parallel opticaltransceiver in accordance with embodiments of the present invention.

FIG. 3 is a diagram showing another optical link of an N×N paralleloptical transceiver in accordance with embodiments of the presentinvention.

FIG. 4 is a diagram showing yet another optical link of an N×N paralleloptical transceiver in accordance with embodiments of the presentinvention.

DETAILED DESCRIPTION

Technical aspects of embodiments of the present invention will be fullyand clearly described in conjunction with the accompanying drawings. Inthe following embodiments, it will be understood that the descriptionsare not intended to limit the invention to these embodiments. Based onthe disclosed embodiments of the present invention, other embodimentsthat can be obtained by one skilled in the art without creative orinventive contribution are considered within the scope of legalprotection given to the present invention.

For example, in one embodiment, the N×N parallel optical transceiver maycomprise a 4×4 parallel optical transceiver. The 4×4 parallel opticaltransceiver may comprise a high frequency printed circuit board, a laserdriving control chip, 4 DFB laser chips, 2 GRIN lenses, a filter, amultimode fiber array and a 1×4 photodiode (PD) chip array. The opticaltransceiver can be employed in 2.5 Gbit/s applications, 10 Gbit/sapplications, and applications at higher transmission speeds.

The printed circuit board is used as a base for fixing or attachingelements, such as laser chips, GRIN lenses, etc. The position of each ofthese elements may be precisely fixed (e.g., by active alignment) toform a predetermined optical link (e.g., in a receiver and/ortransmitter of the transceiver). One end of the printed circuit boardforms a signal input interface, and may include a gold/golden finger. ADFB (distributed feedback) laser is characterized by a built-in Bragggrating, and is in a class of semiconductor lasers that operate on or ina single longitudinal mode. DFB lasers mainly employ semiconductormaterials as the light-generating medium. DFB lasers have excellentspectral characteristics and avoid dispersive effects in long-distancetransmission, so DFB lasers are broadly employed in long-distance,high-speed applications.

FP (Fabry-Perot) lasers have an FP cavity and/or are asemiconductor-based light emitting device. An FP laser is configured toemit coherent light in multiple longitudinal modes, in which the FPcavity is a resonant cavity. Such devices are suited to long-distancecommunications and are characterized by high output optical power, smalldivergence angles, a narrow spectrum and a high modulation rate.

In one design, 4 laser chips emitting laser beams having the samewavelength (e.g., 1310 nm) and a divergence angle of 25-30° are providedand are precisely fixed to the printed circuit board.

Each of the GRIN lenses may comprise a cylindrical optical lens having arefractive index that varies along its radial axis. As a result, theGRIN lenses may smoothly focusing the light from laser devices to themultimode fiber array and/or from the multimode fiber array to thephotodiode array. In the present invention, two GRIN lenses may flank(e.g., be positioned on opposite sides of) the filter and be fixed tothe printed circuit board (e.g., after active alignment). The first GRINlens may have dimensions of 6 mm×4 mm×4 mm, while the second GRIN lensmay have dimensions of 3 mm×4 mm×4 mm. In other words, the first andsecond GRIN lenses may have the same area, but different thicknesses.The optical filter may comprise a wavelength-division filter and/or aband-pass filter that is transparent to laser beams from the transmitterbut reflective (e.g., functioning as a band-elimination filter) to laserbeams entering the transceiver from the multimode fiber array. That is,laser beams from the laser(s) that are focused by the first GRIN lenspass through the filter, while the laser beams received from the fiberarray are focused by the second GRIN lens, reflected by the filter (or asurface thereof) towards the photodiode array, then the received laserbeams are refocused by the second GRIN lens before being received beforebeing received at the photodiode array.

The multimode fiber array may include one or more MTP/MPO standardconnector interfaces, and have one or more dimensions and/orconstructions defined by the MTP and/or MPO standard.

The PD chip array may comprise a linear array (e.g., a 1×4 array). PDsare generally easier to couple to other components in the opticaltransceiver than LDs.

FIG. 1 illustrates an exemplary parallel optical transceiver 10 inaccordance with embodiments of the present invention. For example, aprinted circuit board 15 configured to carry high frequency signalsthereon may include a laser driving chip 20, a laser 30, a first GRINlens 40, an optical and/or bandpass filter 50, a second GRIN lens 60, afiber array 70, and a photoelectric detector 80 thereon. A transmitterin the optical transceiver 10 includes the laser driving chip 20, laser30, first GRIN lens 40, optical and/or bandpass filter 50, second GRINlens 60 and a fiber array 70, and a receiver in the optical transceiver10 includes the fiber array 70, second GRIN lens 60, optical and/orbandpass filter 50, and photoelectric detector 80. The laser 30 maycomprise one or more laser devices and/or chips (preferably N laserdevices and/or chips, where N is an integer ≧2, ≧4, etc.), and thephotoelectric detector 80 may comprise one or more photodiodes(preferably N photodiodes, where N is an integer ≧2, ≧4, etc.). Thus,the parallel optical transceiver 10 may be an N×N parallel opticaltransceiver.

The laser driving chip 20 sends electrical signals (e.g., representingdata) to the laser 30, which generates one or more (e.g., N) opticalsignals that are focused by the first GRIN lens 40. The focused opticalsignal(s) pass through the filter 50, and are refocused by the secondGRIN lens 60 on a location at or in the fiber array 70 (e.g., on asurface of the fibers). Light received by the optical transceiver 10generally has a different wavelength than the light signals generated bythe laser 30. Alternatively or additionally, the light received by theoptical transceiver 10 may have a different polarization type (e.g.,p-polarization or s-polarization) than the light signals generated bythe laser 30. Incoming light from the fiber array 70 is focused by thesecond GRIN lens 60, reflected by the filter 50, refocused by the secondGRIN lens 60 (not shown in FIG. 1), and absorbed or detected by thephotoelectric detector 80. Details of the exemplary parallel opticaltransceiver 10 are discussed below with regard to further Figures.

A First Embodiment

FIG. 2 illustrates an exemplary optical link 100 of the parallel opticaltransceiver (e.g., optical transceiver 10) in accordance withembodiments of the present invention. In the optical link at thetransmitting end (e.g., the transmitter), laser beams 112-118 having thesame wavelength λ₁ are emitted from a plurality of (e.g., 4) DFB laserchips 120 at the same time (e.g., simultaneously). The laser beams112-118 are first focused by the first GRIN lens 40, then they passthrough a wavelength-selective band-pass filter 150. The multiple (e.g.,4) focused laser beams 112′-118′ are refocused by the second GRIN lens60, then the refocused beams respectively enter the channels (e.g., 4channels) in the fiber array 170.

In the optical link at the receiving end (e.g., the receiver), multiple(e.g., 4) laser beams 172-178 having the same wavelength λ₂ from thefour channels in the fiber array 170 are focused by the second GRIN lens60 and reflected by the surface of the wavelength-selective filter 150.The reflected laser beams 172′-178′ are refocused by the second GRINlens 60, then enter the PD chip array 180 (e.g., comprising 4photodiodes or photodiode chips). The exemplary embodiment of FIG. 2 hasthe following attributes:

-   -   1. A single printed circuit board can be used as base and can        support all components (e.g., 10-80 in FIG. 1) thereon. One end        of the printed circuit board includes a signal input interface,        which may be in the form of gold or golden finger.    -   2. Two GRIN lenses 40 and 60 are configured to flank the filter        150 and are fixed to the printed circuit board, for example        after active alignment.    -   3. In the optical link at the transmitting end (e.g.,        transmitter), N (e.g., 4) DFB laser chips 120 are attached to        the printed circuit board (e.g., by flip chip bonding after        active alignment). The DFB laser devices may be spaced apart        from each other by at least about 0.1 mm (e.g., by 0.1 mm), may        have a numerical aperture of at least about 0.4 μm (e.g., by 0.4        μm), and may be spaced apart from the first GRIN lens 40 by a        distance of at least about 0.5 mm (e.g., by 0.5 mm). Laser beams        112-118 having the same wavelength λ₁ emitted from the DFB laser        chips 120 at the same time are first focused by the first GRIN        lens 40 and then pass through the band-pass filter 150 having a        transmissivity of at least 95% (e.g., higher than 95%) to the        wavelength(s) of the beams 112′-118′, then the laser beams        112′-118′ are refocused by the second GRIN lens 60, and the        refocused beams respectively enter the N (e.g., 4) channels in        the fiber array 170.    -   4. In the optical link at the receiving end (e.g., receiver), N        (e.g., 4) laser beams 172-178 having the same wavelength λ₂ from        the N (e.g., 4) channels in the fiber array 170 are focused by        the second GRIN lens 60 and reflected by the surface of the        wavelength-selective and/or bandpass filter 150, and then the N        reflected laser beams are refocused by the second GRIN lens 60        and enter the PD chip array 180. The PD chips may be spaced        apart from each other by at least about 0.15 mm (e.g., 0.15 mm)        in the PD array 180, and the center distance (e.g., the        center-to-center distance) between the PD array 180 and the        fiber array 170 may be at least about 0.7 mm (e.g., 0.7 mm).

A Second Embodiment

FIG. 3 illustrates an exemplary optical link of the parallel opticaltransceiver in accordance with embodiments of the present invention. Inthe parallel optical transceiver, or as shown in FIG. 3, a receiver 200,4 laser beams 172-178 having the same wavelength λ₂ from the fourchannels in the fiber array 170 are focused by the second GRIN lens 60and reflected by the surface of the wavelength-selective and/or bandpassfilter 50, and then the 4 reflected laser beams 172′-178′ are refocusedby the second GRIN lens 60 and enter the PD chip array 180. As above, inembodiments of the present invention related to a FP laser, the onlydifference is that each DFB laser chip is replaced by a FP laser chip,so there is no more tautology.

A Third Embodiment

FIG. 4 illustrates an exemplary optical link of the parallel opticaltransceiver in with embodiments of the present invention. In theparallel optical transceiver, or as shown in FIG. 4, a transmitter 250,laser beams 112-118 having the same wavelength λ₁ emitted simultaneouslyfrom 4 DFB laser chips 110 are first focused by the first GRIN lens 40,then pass through the band pass filter 50, then the 4 laser beams arerefocused by the second GRIN lens 60. After that, the beams respectivelyenter the 4 channels in the fiber array 170.

CONCLUSION/SUMMARY

The invention is intended to cover modifications and equivalents thatmay be included within the spirit and scope of the invention as definedby the present invention.

What is claimed is:
 1. A parallel optical transceiver, comprising: a) a printed circuit board, wherein one end of the printed circuit board includes a signal input interface; b) a laser comprising a plurality of laser chips spaced apart by at least about 0.1 mm and that have a numerical aperture of 0.4 μm on the printed circuit board configured to simultaneously provide laser beams having a first common wavelength; c) a laser driving control chip configured to control the laser, and directly integrated onto or into the printed circuit board; d) a multimode fiber array having N channels, N being an integer of at least 2; e) a band-pass filter configured to allow the laser beams to pass through to the multimode fiber array; f) a first GRIN lens and a second GRIN lens that flank the band-pass filter and are fixed to the printed circuit board, wherein the first GRIN lens is configured to focus the laser beams, and the second GRIN lens is configured to refocus the laser beams on a location in or on the multimode fiber array after the laser beams pass through the band-pass filter; and g) a photodiode array.
 2. The parallel optical transceiver of claim 1, wherein said laser comprises a DFB or FP laser chip, flip chip bonded to the printed circuit board.
 3. The parallel optical transceiver of claim 1, wherein said plurality of laser chips are spaced apart from the first GRIN lens by a distance of at least about 0.5 mm.
 4. The parallel optical transceiver of claim 1, wherein each of said first and second GRIN lenses comprise a cylindrical optical lens having a refractive index that varies along its radial axis.
 5. The parallel optical transceiver of claim 1, wherein said multimode fiber array includes one or more MTP/MPO standard connector interfaces.
 6. The parallel optical transceiver of claim 1, wherein said photodiode array comprises a linear array of N photodiodes.
 7. The parallel optical transceiver of claim 6, wherein said N photodiodes are spaced apart from each other by at least about 0.15 mm, and the center distance between said photodiode array and said multimode fiber array is at least about 0.7 mm.
 8. The parallel optical transceiver of claim 1, wherein said signal input interface comprises a gold or golden finger.
 9. The parallel optical transceiver of claim 1, comprising a transmitting end having a first optical link, and a receiving end having a second optical link.
 10. The parallel optical transceiver of claim 1, wherein said printed circuit board is configured to carry high frequency signals.
 11. A parallel optical transceiver, comprising: a) a printed circuit board, wherein one end of the printed circuit board includes a signal input interface; b) a laser on the printed circuit board configured to simultaneously provide laser beams having a first common wavelength; c) a laser driving control chip configured to control the laser, and directly integrated onto or into the printed circuit board; d) a multimode fiber array having N channels, N being an integer of at least 2; e) a band-pass filter configured to allow the laser beams to pass through to the multimode fiber array; f) a first GRIN lens and a second GRIN lens that flank the band-pass filter and are fixed to the printed circuit board, wherein the first GRIN lens is configured to focus the laser beams, and the second GRIN lens is configured to refocus the laser beams on a location in or on the multimode fiber array after the laser beams pass through the band-pass filter; and g) a photodiode array comprising a linear array of N photodiodes, wherein said N photodiodes are spaced apart from each other by at least about 0.15 mm, and the center distance between said photodiode array and said multimode fiber array is at least about 0.7 mm.
 12. The parallel optical transceiver of claim 11, wherein said laser comprises a plurality of laser chips spaced apart by at least about 0.1 mm and that have a numerical aperture of 0.4 pm.
 13. The parallel optical transceiver of claim 11, wherein the first GRIN lens focuses N received laser beams from channels in the multimode fiber array, the N received laser beams have a same wavelength, a surface of the band-pass filter reflects the N focused received laser beams towards the photodiode array, and the second GRIN lens refocuses the N reflected laser beams.
 14. A parallel optical transceiver, the optical transceiver comprising: a) a printed circuit board forming a base, wherein one end of the printed circuit board includes a signal input interface; b) a laser driving control chip; c) a laser; d) a multimode fiber array having N channels, N being an integer of at least 2; e) a first GRIN lens fixed to the printed circuit board; f) a linear array of N photodiodes, wherein said N photodiodes are spaced apart from each other by at least about 0.15 mm, and the center distance between said photodiode array and said multimode fiber array is at least about 0.7 mm; g) an optical filter fixed to the printed circuit board, configured to reflect N laser beams having a common wavelength from the N channels in the multimode fiber array towards the linear array of N photodiodes; and h) a second GRIN lens configured to focus the N received laser beams from channels in the multimode fiber array.
 15. The parallel optical transceiver of claim 14, wherein said laser simultaneously provides N laser beams having a different common wavelength, and said first GRIN lens focuses the N laser beams having the different common wavelength, the band-pass filter allows the N laser beams having the different common wavelength to pass through to the second GRIN lens, then the second GRIN lens refocuses the N laser beams having the different common wavelength on a location on or in the multimode fiber array.
 16. The parallel optical transceiver of claim 14, wherein said signal input interface comprises a gold or golden finger.
 17. The parallel optical transceiver of claim 14, wherein said printed circuit board is configured to carry high frequency signals.
 18. An N×N parallel optical transceiver, the optical transceiver comprising: a) a printed circuit board having one end that includes a signal input interface; b) a laser driving control chip, c) a plurality of laser chips spaced apart by at least about 0.1 mm and that have a numerical aperture of 0.4 μm, attached to the printed circuit board and configured to simultaneously provide N laser beams having a first common wavelength, N being an integer of at least 2; d) a first GRIN lens configured to focus the N laser beams; e) an optical band-pass filter fixed to the printed circuit board and transparent to light having the first common wavelength; f) a multimode fiber array having N channels therein; and g) a second GRIN lens, configured to refocus the N laser beams on locations on or in the N channels of the multimode fiber array, wherein one of the first and second GRIN lenses is fixed to the printed circuit board.
 19. The N×N optical transceiver of claim 18, further comprising an array of N photodiodes, wherein the second GRIN lens focuses N received laser beams from channels in the multimode fiber array, the N received laser beams have a second common wavelength, the optical band-pass filter reflects the N focused received laser beams towards the photodiode array, and the second GRIN lens refocuses the N reflected laser beams.
 20. The parallel optical transceiver of claim 18, wherein said signal input interface comprises a gold or golden finger.
 21. The parallel optical transceiver of claim 18, wherein said printed circuit board is configured to carry high frequency signals. 